<!DOCTYPE html>
<html>
  <head>
    <title>negative mspace</title>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
  </head>
  <body>
    <p>
      <math>
	<mrow>
	  <mspace width="2em" height="1em" mathbackground="red"></mspace>
	  <mspace width="-1em"/>
	  <mspace width="1em" height="1em" mathbackground="blue"></mspace>
	</mrow>
      </math>
    </p>
    <p>
      <math dir="rtl">
	<mrow>
	  <mspace width="2em" height="1em" mathbackground="red"></mspace>
	  <mspace width="-1em"/>
	  <mspace width="1em" height="1em" mathbackground="blue"></mspace>
	</mrow>
      </math>
    </p>
  </body>
</html>
